check engine light
 

have just put in new crankshaft sensor and thought all was well. check engine light still comes on and gas cap is secure. what else could it be?

Could be anything. What code is it?

Why did you think CPS?

Scan it and see what codes come up. You may have not licked all the problems by replacing that part. Thats why the onboard diagnostic is there for to pinpoint the problem.

CEL on ML
 

Mine CEL came on if the fuel was low but not low enough to make low fuel light glow.

Here, in no particular order, are some of the components/problems I've seen cause CEL's on late model MB's.

1. Mass Air Flow Sensor
2. Oxygen Sensor (you've got four)
3. Purge Valve
4. Charcoal Canister Shut-off Valve
5. Ignition Coil(s)/Wires
6. EGR Valve (lookout for clogs)
7. Air Injection System (a "lazy" O2 sensor could throw this code, be careful)
8. Manifold Pressure Sensor (very rare)
9. Transmission (since there's no Transmission warning light, the CEL is used)

Keep in mind that some of the above mentioned components can fail either electrically, or mechanically. #'s 3, 4, and 6 all have internal moving parts. They may recieve the correct signal, but can still fail to do their job.

The list goes on and on. Have the car checked for fault codes and post the results.